1. Field of the Invention
The present invention relates to vehicular airbag cushions. More specifically, the present invention relates to a load path control which redirects a load force in an inflating airbag cushion.
2. Technical Background
Inflatable safety restraint devices, or airbags modules, are now required by law to be installed in most new vehicles. Inflatable vehicle occupant safety restraint modules, or airbag modules, are mandatory on most new vehicles. Airbag modules commonly contain a collision sensor, an inflator, and an airbag cushion. In the event of an accident, a collision sensor such as an accelerometer, measures abnormal deceleration and triggers the inflator by means of an electronic signal. The inflator is generally a pyrotechnic device which produces gas. The inflator is connected to the airbag cushion and inflates the airbag cushion through an opening.
Prior to inflation, the airbag cushions are housed in an uninflated and folded condition to minimize space requirements. Typically the airbag module is housed in the steering wheel on the driver's side of a vehicle and in the dashboard on the passenger side of a vehicle. Upon receipt of the signal from the collision sensor, the inflator rapidly produces a quantity of inflation fluid or gas which inflates the cushion and protects the passenger from harmful impact with the interior of the car.
The airbag cushion and inflator must be securely mounted to the vehicle for proper function and positioning of the airbag cushion. Therefore, airbag modules typically have a housing which can be securely mounted within the dashboard or steering column. The housing serves the dual purpose of protecting the airbag cushion from damage in the stored configuration and securely holding the airbag cushion in the inflated configuration.
The airbag cushion is typically secured to the housing by a retaining member. The retaining member can be slid into the inflation opening of the airbag cushion. Adjacent the inflation opening, the airbag cushion has an attachment region which has a plurality of attachment points through which the airbag cushion can be attached to the housing. Generally, the attachment points are holes within the attachment region which are configured to receive fasteners. The fasteners run from the retaining member, though attachment points in the airbag cushion, and to the housing. As the fasteners, which are typically bolts, are tightened the airbag cushion is sandwiched between the housing and the retaining member. Thus, the airbag cushion is firmly attached to the housing and remains in position during inflation.
However, when the inflator is activated, the airbag cushion inflates with great force and rapidity. This large force places significant stress on the attachment region of the airbag cushion. This stress may cause the airbag cushion to tear out from under the retaining member. Such tearing can cause the inflation gas to flow outside of the cushion, limiting the efficacy of the restraint device. Additionally, a torn airbag may deflate before fully protecting an occupant from impact.
To overcome some of the issues associated with airbags tearing out from the retaining member under the stress from inflation, the attachment region can be reinforced with one or more layers of reinforcement material. Such material is typically the same material as used in the remainder of the airbag cushion, but may be another material selected for its strength. The reinforcement layers are secured to the airbag cushion by sewing, gluing, welding, weaving, and like attachment methods.
Airbag modules with reinforced attachment regions exhibit improved ability to withstand the load forces of the inflating airbag. However, when the retainer member and airbag cushion are secured to the housing, the clamping force applied to the sandwiched attachment region of the airbag is unequal. In particular, a high clamping force is applied in the region adjacent the fasteners, and a low clamping force is applied in the region between fasteners. This difference in clamping force is a function of the limited stiffness of the retainer member. The airbag cushion can more readily tear out from the areas with a low clamping force creating the same problems with gas loss and airbag integrity discussed above.
The approaches that are currently used to overcome the tearing associated with the low clamp areas increase the cost and weight of the airbag module. Two of the approaches commonly used are the use additional fasteners and the addition of extra layers of reinforcement material. The additional fasteners increase the number of high clamp areas and therefore reduce the size of the low clamp areas. Likewise, the addition of more layers of reinforcement material results in a reduction in the size of the low clamp area. The cost of each airbag unit is increased by the addition of fasteners and layers of reinforcement material. Additionally, each of these approaches adds weight to the airbag module which increases the cost associated with manufacture, shipping, and installation of the airbag modules. Moreover, the use of extra fasteners can increase the time and difficulty associated with manufacture and installation of the airbag modules.
In light of the foregoing, it would be an advancement in the art to provide an airbag module that would be resistant to tearing under the stress of inflation. It would be an additional advancement if the airbag module were resistant to tearing without increasing the cost or manufacturing the airbag module. It would be a further advancement if the airbag module were resistant to tearing without increasing the weight of the airbag module. It would be a further advancement if the airbag module were resistant to tearing without the use of additional fasteners or layers of reinforcement material. It would be an additional advancement if the airbag module could transfer the force of the inflating airbag cushion from a low clamp area to a high clamp area. Such an airbag module is disclosed and claimed herein.